#define __KERNEL__		/* kernel code */ 
#define MODULE			/* always as a module */ 

#include <linux/module.h>
#include <linux/fs.h>		/* for file_operations */

#define DEFAULT_MAJOR 121

MODULE_AUTHOR("Guto");
MODULE_DESCRIPTION("Just another dummy module to play with");

/* MODULE PARAMETERS */
static int dev = DEFAULT_MAJOR;
MODULE_PARM(dev,"i");
MODULE_PARM_DESC(dev,"Major device number");

/* PROTOTYPES */
static int init_module(void); 
static void cleanup_module(void);
static int dummy_open(struct inode * inode, struct file * filp);
static int dummy_close(struct file * filp);
static ssize_t dummy_read(struct file * filp, char * buf, size_t count,
			  loff_t * offset);

/* FILE OPERATIONS */
static struct file_operations dummy_fops = {
    owner:    NULL,
    llseek:   NULL,
    read:     &dummy_read,
    write:    NULL,
    readdir:  NULL,
    poll:     NULL,
    ioctl:    NULL,
    mmap:     NULL,
    open:     &dummy_open,
    flush:    &dummy_close,
    release:  NULL,
    fsync:    NULL,
    fasync:   NULL,
    lock:     NULL,
    readv:    NULL,
    writev:   NULL,
    sendpage: NULL,
    get_unmapped_area: NULL
};

int init_module(void)
{
    printk("Loading module dummy with major=%d\n", dev);

    /* Set field owner of file_operations to this module */
    SET_MODULE_OWNER(&dummy_fops);

    /* Register the device driver */
    return register_chrdev(dev, "dummy", &dummy_fops);
}

void cleanup_module(void)
{
    printk("Unloading module dummy\n");

    /* Unregister the device driver */
    unregister_chrdev(dev, "dummy");
}

int dummy_open(struct inode * inode, struct file * filp)
{
    int unit;

    /* Get device's minor number */
    unit = MINOR(inode->i_rdev);

    printk("dummy_open(unit=%d)\n", unit);

    return 0;
}

int dummy_close(struct file * filp)
{
    int unit;

    /* Get device's minor number */
    unit = MINOR(filp->f_dentry->d_inode->i_rdev);

    printk("dummy_close(unit=%d)\n", unit);

    return 0;
}

ssize_t dummy_read(struct file * filp, char * buf, size_t count,
		   loff_t * offset)
{
    int unit, i;

    /* Get device's minor number */
    unit = MINOR(filp->f_dentry->d_inode->i_rdev);

    printk("dummy_read(unit=%d,buf=%p,cnt=%d,off=%d)\n", unit, buf, count,
	   *offset);

    /* Produces a dummy output */
    for(i = 0; i < count; i++)
	buf[i] = 'D';
    
    return count;
}